1. Field of the Invention
The present invention relates to an electric power steering apparatus equipped with an electric motor for outputting assist torque to a steering wheel of a vehicle, and a drive control unit for controlling the driving of an output shaft of the electric motor.
2. Description of the Related Art
In the past, there has been known an electric power steering apparatus in which a motor housing of an electric motor, which is adapted to output an assist torque to a steering wheel of a vehicle, and a drive housing of a drive control unit, which serves to control the driving of an output shaft of the electric motor, are fixedly secured to each other at a mating surface in a surface to surface contact manner, and in which the motor housing and a gear housing that receives therein a gear connected with the output shaft of the electric motor are coupled with each other on the one and same axis (see, for example, a first patent document: Japanese Patent No. 3,638,269 (FIG. 3, paragraph No. 0072)).
In such an electric power steering apparatus, the electric motor and the drive control unit are integrated with each other, so that the entire apparatus can be reduced in size, and the length of electrical wiring that electrically connects between the electric motor and the drive control unit can be shortened as much as possible, as a consequence of which the production cost thereof can be reduced due to the reduction in the cost of materials, etc., or the reduction of electric power loss, noise and so on can also be achieved.
The electric power steering apparatus as constructed above is fitted to a vehicle body in a vehicle production line in a factory as a power steering mechanism that is formed integral with the steering wheel, a column shaft, etc.
In general, in case where the entire electric power steering apparatus is to be replaced by a new one, the power steering mechanism including the electric power steering apparatus is first detached or dismounted from the vehicle body, and the electric power steering apparatus is then replaced by the new one.
In the replacement of an electric power steering apparatus, only the drive control unit built therein, which includes a lot of semiconductor parts and has a high failure rate, is sometimes desired to be replaced. In this case, in the electric power steering apparatus, a location of connection at which a connecting portion of the electric motor and a connecting portion of the drive control unit are connected with each other by screws, is inside a joint location of the motor housing and the gear housing, so there has been the following problem. That is, it is necessary to take the trouble of once detaching or dismounting the electric power steering apparatus from the gear housing of the power steering mechanism, then removing the screws in the electrically connecting portions through an opening portion of the motor housing at a gear housing side, thereafter detaching the drive control unit from the electric motor, and replacing it with a new one.